PEGylated crushed gold shell-radiolabeled core nanoballs for in vivo tumor imaging with dual positron emission tomography and Cerenkov luminescent imaging

Metallic nanoparticles unveiled: Synthesis, characterization, and their environmental, medicinal, and agricultural applications

Metallic nanoparticles (MNPs) have attracted great interest among scientists and researchers for years due to their unique optical, physiochemical, biological, and magnetic properties. As a result, MNPs have been widely utilized across a variety of scientific fields, including biomedicine, agriculture, electronics, food, cosmetics, and the environment. In this regard, the current review article offers a comprehensive overview of recent studies on the synthesis of MNPs (metal and metal oxide nanoparticles), outlining the benefits and drawbacks of chemical, physical, and biological methods. However, the biological synthesis of MNPs is of great importance considering the biocompatibility and biological activity of certain MNPs. A variety of characterization techniques, including X-ray diffraction, transmission electron microscopy, UV-visible spectroscopy, scanning electron microscopy, dynamic light scattering, atomic force microscopy, Fourier transform infrared spectroscopy, and others, have been discussed in depth to gain deeper insights into the unique structural and spectroscopic properties of MNPs. Furthermore, their unique properties and applications in the fields of medicine, agriculture, and the environment are summarized and deeply discussed. Finally, the main challenges and limitations of MNPs synthesis and applications, as well as their future prospects have also been discussed.

Methods for Radiolabelling Nanoparticles: PET Use (Part 2)

The use of radiolabelled nanoparticles (NPs) is a promising nuclear medicine tool for diagnostic and therapeutic purposes. Thanks to the heterogeneity of their material (organic or inorganic) and their unique physical and chemical characteristics, they are highly versatile for their use in several medical applications. In particular, they have shown interesting results as radiolabelled probes for positron emission tomography (PET) imaging. The high variability of NP types and the possibility to use several isotopes in the radiolabelling process implies different radiolabelling methods that have been applied over the previous years. In this review, we compare and summarize the different methods for NP radiolabelling with the most frequently used PET isotopes.

Significance of Capping Agents of Colloidal Nanoparticles from the Perspective of Drug and Gene Delivery, Bioimaging, and Biosensing: An Insight

The over-growth and coagulation of nanoparticles is prevented using capping agents by the production of stearic effect that plays a pivotal role in stabilizing the interface. This strategy of coating the nanoparticles’ surface with capping agents is an emerging trend in assembling multipurpose nanoparticles that is beneficial for improving their physicochemical and biological behavior. The enhancement of reactivity and negligible toxicity is the outcome. In this review article, an attempt has been made to introduce the significance of different capping agents in the preparation of nanoparticles. Most importantly, we have highlighted the recent progress, existing roadblocks, and upcoming opportunities of using surface modified nanoparticles in nanomedicine from the drug and gene delivery, bioimaging, and biosensing perspectives.

Recent Advances in Nanomaterials for Diagnosis, Treatments, and Neurorestoration in Ischemic Stroke

Stroke is a major public health issue, corresponding to the second cause of mortality and the first cause of severe disability. Ischemic stroke is the most common type of stroke, accounting for 87% of all strokes, where early detection and clinical intervention are well known to decrease its morbidity and mortality. However, the diagnosis of ischemic stroke has been limited to the late stages, and its therapeutic window is too narrow to provide rational and effective treatment. In addition, clinical thrombolytics suffer from a short half-life, inactivation, allergic reactions, and non-specific tissue targeting. Another problem is the limited ability of current neuroprotective agents to promote recovery of the ischemic brain tissue after stroke, which contributes to the progressive and irreversible nature of ischemic stroke and also the severity of the outcome. Fortunately, because of biomaterials’ inherent biochemical and biophysical properties, including biocompatibility, biodegradability, renewability, nontoxicity, long blood circulation time, and targeting ability. Utilization of them has been pursued as an innovative and promising strategy to tackle these challenges. In this review, special emphasis will be placed on the recent advances in the study of nanomaterials for the diagnosis and therapy of ischemic stroke. Meanwhile, nanomaterials provide much promise for neural tissue salvage and regeneration in brain ischemia, which is also highlighted.

PET/Fluorescence Imaging: An Overview of the Chemical Strategies to Build Dual Imaging Tools

Molecular imaging is a biomedical research discipline that has quickly emerged to afford the observation, characterization, monitoring, and quantification of biomarkers and biological processes in living organism. It covers a large array of imaging techniques, each of which provides anatomical, functional, or metabolic information. Multimodality, as the combination of two or more of these techniques, has proven to be one of the best options to boost their individual properties, hence offering unprecedented tools for human health. In this review, we will focus on the combination of positron emission tomography and fluorescence imaging from the specific perspective of the chemical synthesis of dual imaging agents. Based on a detailed analysis of the literature, this review aims at giving a comprehensive overview of the chemical strategies implemented to build adequate imaging tools considering radiohalogens and radiometals as positron emitters, fluorescent dyes mostly emitting in the NIR window and all types of targeting vectors.

Recent Advances in Brachytherapy Using Radioactive Nanoparticles: An Alternative to Seed-Based Brachytherapy

Interstitial brachytherapy (BT) is generally used for the treatment of well-confined solid tumors. One example of this is in the treatment of prostate tumors by permanent placement of radioactive seeds within the prostate gland, where low doses of radiation are delivered for several months. However, successful implementation of this technique is hampered due to several posttreatment adverse effects or symptoms and operational and logistical complications associated with it. Recently, with the advancements in nanotechnology, radioactive nanoparticles (radio-NPs) functionalized with tumor-specific biomolecules, injected intratumorally, have been reported as an alternative to seed-based BT. Successful treatment of solid tumors using radio-NPs has been reported in several preclinical studies, on both mice and canine models. In this article, we review the recent advancements in the synthesis and use of radio-NPs as a substitute to seed-based BT. Here, we discuss the limitations of current seed-based BT and advantages of radio-NPs for BT applications. Recent progress on the types of radio-NPs, their features, synthesis methods, and delivery techniques are discussed. The last part of the review focuses on the currently used dosimetry protocols and studies on the dosimetry of nanobrachytherapy applications using radio-NPs. The current challenges and future research directions on the role of radio-NPs in BT treatments are also discussed.

Gold nanoparticles meet medical radionuclides

Thanks to their unique optical and physicochemical properties, gold nanoparticles have gained increased interest as radiosensitizing, photothermal therapy and optical imaging agents to enhance the effectiveness of cancer detection and therapy. Furthermore, their ability to carry multiple medically relevant radionuclides broadens their use to nuclear medicine SPECT and PET imaging as well as targeted radionuclide therapy. In this review, we discuss the radiolabeling process of gold nanoparticles and their use in (multimodal) nuclear medicine imaging to better understand their specific distribution, uptake and retention in different in vivo cancer models. In addition, radiolabeled gold nanoparticles enable image-guided therapy is reviewed as well as the enhancement of targeted radionuclide therapy and nanobrachytherapy through an increased dose deposition and radiosensitization, as demonstrated by multiple Monte Carlo studies and experimental in vitro and in vivo studies.

A review of recent and emerging approaches for the clinical application of Cerenkov luminescence imaging

Cerenkov luminescence (CL) is a blue-weighted emission of light produced by a vast array of clinically approved radioisotopes and LINAC accelerators. When β particles (emitted during the decay of radioisotopes) are present in a medium such as water or tissue, they are able to travel faster than the speed of light in that medium and in doing so polarize the molecules around them. Once the particle has left the local area, the polarized molecules relax and return to their baseline state releasing the additional energy as light (luminescence). This blue glow has commonly been used to determine the output of nuclear power plant cores and, in recent years, has found traction in the preclinical and clinical imaging field. This brief review will discuss the technology which has enabled the emergence of the biomedical Cerenkov imaging field, recent pre-clinical studies with potential clinical translation of Cerenkov luminescence imaging (CLI) and the current clinical implementations of the method. Finally, an outlook is given as to the direction in which the field is heading.

Radiopharmaceutical and Eu3+ doped gadolinium oxide nanoparticles mediated triple-excited fluorescence imaging and image-guided surgery

Cerenkov luminescence imaging (CLI) is a novel optical imaging technique that has been applied in clinic using various radionuclides and radiopharmaceuticals. However, clinical application of CLI has been limited by weak optical signal and restricted tissue penetration depth. Various fluorescent probes have been combined with radiopharmaceuticals for improved imaging performances. However, as most of these probes only interact with Cerenkov luminescence (CL), the low photon fluence of CL greatly restricted it's interaction with fluorescent probes for in vivo imaging. Therefore, it is important to develop probes that can effectively convert energy beyond CL such as β and γ to the low energy optical signals. In this study, a Eu3+ doped gadolinium oxide (Gd2O3:Eu) was synthesized and combined with radiopharmaceuticals to achieve a red-shifted optical spectrum with less tissue scattering and enhanced optical signal intensity in this study. The interaction between Gd2O3:Eu and radiopharmaceutical were investigated using 18F-fluorodeoxyglucose (18F-FDG). The ex vivo optical signal intensity of the mixture of Gd2O3:Eu and 18F-FDG reached 369 times as high as that of CLI using 18F-FDG alone. To achieve improved biocompatibility, the Gd2O3:Eu nanoparticles were then modified with polyvinyl alcohol (PVA), and the resulted nanoprobe PVA modified Gd2O3:Eu (Gd2O3:Eu@PVA) was applied in intraoperative tumor imaging. Compared with 18F-FDG alone, intraoperative administration of Gd2O3:Eu@PVA and 18F-FDG combination achieved a much higher tumor-to-normal tissue ratio (TNR, 10.24 ± 2.24 vs. 1.87 ± 0.73, P = 0.0030). The use of Gd2O3:Eu@PVA and 18F-FDG also assisted intraoperative detection of tumors that were omitted by preoperative positron emission tomography (PET) imaging. Further experiment of image-guided surgery demonstrated feasibility of image-guided tumor resection using Gd2O3:Eu@PVA and 18F-FDG. In summary, Gd2O3:Eu can achieve significantly optimized imaging property when combined with 18F-FDG in intraoperative tumor imaging and image-guided tumor resection surgery. It is expected that the development of the Gd2O3:Eu nanoparticle will promote investigation and application of novel nanoparticles that can interact with radiopharmaceuticals for improved imaging properties. This work highlighted the impact of the nanoprobe that can be excited by radiopharmaceuticals emitting CL, β, and γ radiation for precisely imaging of tumor and intraoperatively guide tumor resection.

Radiolabelling of nanomaterials for medical imaging and therapy

Nanomaterials offer unique physical, chemical and biological properties of interest for medical imaging and therapy. Over the last two decades, there has been an increasing effort to translate nanomaterial-based medicinal products (so-called nanomedicines) into clinical practice and, although multiple nanoparticle-based formulations are clinically available, there is still a disparity between the number of pre-clinical products and those that reach clinical approval. To facilitate the efficient clinical translation of nanomedicinal-drugs, it is important to study their whole-body biodistribution and pharmacokinetics from the early stages of their development. Integrating this knowledge with that of their therapeutic profile and/or toxicity should provide a powerful combination to efficiently inform nanomedicine trials and allow early selection of the most promising candidates. In this context, radiolabelling nanomaterials allows whole-body and non-invasive in vivo tracking by the sensitive clinical imaging techniques positron emission tomography (PET), and single photon emission computed tomography (SPECT). Furthermore, certain radionuclides with specific nuclear emissions can elicit therapeutic effects by themselves, leading to radionuclide-based therapy. To ensure robust information during the development of nanomaterials for PET/SPECT imaging and/or radionuclide therapy, selection of the most appropriate radiolabelling method and knowledge of its limitations are critical. Different radiolabelling strategies are available depending on the type of material, the radionuclide and/or the final application. In this review we describe the different radiolabelling strategies currently available, with a critical vision over their advantages and disadvantages. The final aim is to review the most relevant and up-to-date knowledge available in this field, and support the efficient clinical translation of future nanomedicinal products for in vivo imaging and/or therapy.

Radiolabeled Gold Nanoparticles for Imaging and Therapy of Cancer

In the Last decades, nanotechnology has provided novel and alternative methodologies and tools in the field of medical oncology, in order to tackle the issues regarding the control and treatment of cancer in modern society. In particular, the use of gold nanoparticles (AuNPs) in radiopharmaceutical development has provided various nanometric platforms for the delivery of medically relevant radioisotopes for SPECT/PET diagnosis and/or radionuclide therapy. In this review, we intend to provide insight on the methodologies used to obtain and characterize radiolabeled AuNPs while reporting relevant examples of AuNPs developed during the last decade for applications in nuclear imaging and/or radionuclide therapy, and highlighting the most significant preclinical studies and results.

Nanoparticles for Cerenkov and Radioluminescent Light Enhancement for Imaging and Radiotherapy

Cerenkov luminescence imaging and Cerenkov photodynamic therapy have been developed in recent years to exploit the Cerenkov radiation (CR) generated by radioisotopes, frequently used in Nuclear Medicine, to diagnose and fight cancer lesions. For in vivo detection, the endpoint energy of the radioisotope and, thus, the total number of the emitted Cerenkov photons, represents a very important variable and explains why, for example, ⁶⁸Ga is better than ¹⁸F. However, it was also found that the scintillation process is an important mechanism for light production. Nanotechnology represents the most important field, providing nanosctructures which are able to shift the UV-blue emission into a more suitable wavelength, with reduced absorption, which is useful especially for in vivo imaging and therapy applications. Nanoparticles can be made, loaded or linked to fluorescent dyes to modify the optical properties of CR radiation. They also represent a useful platform for therapeutic agents, such as photosensitizer drugs for the production of reactive oxygen species (ROS). Generally, NPs can be spaced by CR sources; however, for in vivo imaging applications, NPs bound to or incorporating radioisotopes are the most interesting nanocomplexes thanks to their high degree of mutual colocalization and the reduced problem of false uptake detection. Moreover, the distance between the NPs and CR source is crucial for energy conversion. Here, we review the principal NPs proposed in the literature, discussing their properties and the main results obtained by the proponent experimental groups.

Application of Nanomaterials in Biomedical Imaging and Cancer Therapy

Nanomaterials, such as nanoparticles, nanorods, nanosphere, nanoshells, and nanostars, are very commonly used in biomedical imaging and cancer therapy. They make excellent drug carriers, imaging contrast agents, photothermal agents, photoacoustic agents, and radiation dose enhancers, among other applications. Recent advances in nanotechnology have led to the use of nanomaterials in many areas of functional imaging, cancer therapy, and synergistic combinational platforms. This review will systematically explore various applications of nanomaterials in biomedical imaging and cancer therapy. The medical imaging modalities include magnetic resonance imaging, computed tomography, positron emission tomography, single photon emission computerized tomography, optical imaging, ultrasound, and photoacoustic imaging. Various cancer therapeutic methods will also be included, including photothermal therapy, photodynamic therapy, chemotherapy, and immunotherapy. This review also covers theranostics, which use the same agent in diagnosis and therapy. This includes recent advances in multimodality imaging, image-guided therapy, and combination therapy. We found that the continuous advances of synthesis and design of novel nanomaterials will enhance the future development of medical imaging and cancer therapy. However, more resources should be available to examine side effects and cell toxicity when using nanomaterials in humans.

Simultaneous in vivo PET/MRI using fluorine-18 labeled Fe3O4@Al(OH)3 nanoparticles: comparison of nanoparticle and nanoparticle-labeled stem cell distribution

BACKGROUND

Mesenchymal stem cells (MSCs) have shown potential for treatment of different diseases. However, their working mechanism is still unknown. To elucidate this, the non-invasive and longitudinal tracking of MSCs would be beneficial. Both iron oxide-based nanoparticles (Fe₃O₄ NPs) for magnetic resonance imaging (MRI) and radiotracers for positron emission tomography (PET) have shown potential as in vivo cell imaging agents. However, they are limited by their negative contrast and lack of spatial information as well as short half-life, respectively. In this proof-of-principle study, we evaluated the potential of Fe₃O₄@Al(OH)₃ NPs as dual PET/MRI contrast agents, as they allow stable binding of [¹⁸F]F^- ions to the NPs and thus, NP visualization and quantification with both imaging modalities.

RESULTS

¹⁸F-labeled Fe₃O₄@Al(OH)₃ NPs (radiolabeled NPs) or mouse MSCs (mMSCs) labeled with these radiolabeled NPs were intravenously injected in healthy C57Bl/6 mice, and their biodistribution was studied using simultaneous PET/MRI acquisition. While liver uptake of radiolabeled NPs was seen with both PET and MRI, mMSCs uptake in the lungs could only be observed with PET. Even some initial loss of fluoride label did not impair NPs/mMSCs visualization. Furthermore, no negative effects on blood cell populations were seen after injection of either the NPs or mMSCs, indicating good biocompatibility.

CONCLUSION

We present the application of novel ¹⁸F-labeled Fe₃O₄@Al(OH)₃ NPs as safe cell tracking agents for simultaneous PET/MRI. Combining both modalities allows fast and easy NP and mMSC localization and quantification using PET at early time points, while MRI provides high-resolution, anatomic background information and long-term NP follow-up, hereby overcoming limitations of the individual imaging modalities.

Gold Nanoparticles and Nanorods in Nuclear Medicine: A Mini Review

In the last decade, many innovative nanodrugs have been developed, as well as many nanoradiocompounds that show amazing features in nuclear imaging and/or radiometabolic therapy. Their potential uses offer a wide range of possibilities. It can be possible to develop nondimensional systems of existing radiopharmaceuticals or build engineered systems that combine a nanoparticle with the radiopharmaceutical, a tracer, and a target molecule, and still develop selective nanodetection systems. This review focuses on recent advances regarding the use of gold nanoparticles and nanorods in nuclear medicine. The up-to-date advancements will be shown concerning preparations with special attention on the dimensions and functionalizations that are most used to attain an enhanced performance of gold engineered nanomaterials. Many ideas are offered regarding recent in vitro and in vivo studies. Finally, the recent clinical trials and applications are discussed.

Crushed Gold Shell Nanoparticles Labeled with Radioactive Iodine as a Theranostic Nanoplatform for Macrophage-Mediated Photothermal Therapy

Plasmonic nanostructure-mediated photothermal therapy (PTT) has proven to be a promising approach for cancer treatment, and new approaches for its effective delivery to tumor lesions are currently being developed. This study aimed to assess macrophage-mediated delivery of PTT using radioiodine-124-labeled gold nanoparticles with crushed gold shells (¹²⁴I-Au@AuCBs) as a theranostic nanoplatform. ¹²⁴I-Au@AuCBs exhibited effective photothermal conversion effects both in vitro and in vivo and were efficiently taken up by macrophages without cytotoxicity. After the administration of ¹²⁴I-Au@AuCB-labeled macrophages to colon tumors, intensive signals were observed at tumor lesions, and subsequent in vivo PTT with laser irradiation yielded potent antitumor effects. The results indicate the considerable potential of ¹²⁴I-Au@AuCBs as novel theranostic nanomaterials and the prominent advantages of macrophage-mediated cellular therapies in treating cancer and other diseases.

Chlorotoxin peptide-functionalized polyethylenimine-entrapped gold nanoparticles for glioma SPECT/CT imaging and radionuclide therapy

BACKGROUND

Malignant glioma is the most common and deadliest brain cancer due to the obstacle from indistinct tumor margins for surgical excision and blood brain barrier (BBB) for chemotherapy. Here, we designed and prepared multifunctional polyethylenimine-entrapped gold nanoparticles (Au PENPs) for targeted SPECT/CT imaging and radionuclide therapy of glioma.

RESULTS

Polyethylenimine was selected as a template for sequential modification with polyethylene glycol (PEG), glioma-specific peptide (chlorotoxin, CTX) and 3-(4-hydroxyphenyl)propionic acid-OSu (HPAO), and were then used to entrap gold nanoparticles (Au NPs). After 131I radiolabeling via HPAO, the 131I-labeded CTX-functionalized Au PENPs as a multifunctional glioma-targeting nanoprobe were generated. Before 131I radiolabeling, the CTX-functionalized Au PENPs exhibited a uniform size distribution, favorable X-ray attenuation property, desired water solubility, and cytocompatibility in the given Au concentration range. The 131I-labeled CTX-functionalized Au PENPs showed high radiochemical purity and stability, and could be used as a nanoprobe for the targeted SPECT/CT imaging and radionuclide therapy of glioma cells in vitro and in vivo in a subcutaneous tumor model. Owing to the unique biological properties of CTX, the developed nanoprobe was able to cross the BBB and specifically target glioma cells in a rat intracranial glioma model.

CONCLUSIONS

Our results indicated that the formed nanosystem had the significant potential to be applied for glioma targeted diagnosis and therapy.

External stimulus responsive inorganic nanomaterials for cancer theranostics

Cancer is a highly intelligent system of cells, that works together with the body to thrive and subsequently overwhelm the host in order for its survival. Therefore, treatment regimens should be equally competent to outsmart these cells. Unfortunately, it is not the case with current therapeutic practices, the reason why it is still one of the most deadly adversaries and an imposing challenge to healthcare practitioners and researchers alike. With rapid nanotechnological interventions in the medical arena, the amalgamation of diagnostic and therapeutic functionalities into a single platform, theranostics provides a never before experienced hope of enhancing diagnostic accuracy and therapeutic efficiency. Additionally, the ability of these nanotheranostic agents to perform their actions on-demand, i.e. can be controlled by external stimulus such as light, magnetic field, sound waves and radiation has cemented their position as next generation anti-cancer candidates. Numerous reports exist of such stimuli-responsive theranostic nanomaterials against cancer, but few have broken through to clinical trials, let alone clinical practice. This review sheds light on the pros and cons of a few such theranostic nanomaterials, especially inorganic nanomaterials which do not require any additional chemical moieties to initiate the stimulus. The review will primarily focus on preclinical and clinical trial approved theranostic agents alone, describing their success or failure in the respective stages.